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Grain Boundaries Act as Solid Walls for Charge Carrier Diffusion in Large Crystal MAPI Thin Films

Lookup NU author(s): Dr Pablo Docampo

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Abstract

© 2018 American Chemical Society. Micro- and nanocrystalline methylammonium lead iodide (MAPI)-based thin-film solar cells today reach power conversion efficiencies of over 20%. We investigate the impact of grain boundaries on charge carrier transport in large crystal MAPI thin films using time-resolved photoluminescence (PL) microscopy and numerical model calculations. Crystal sizes in the range of several tens of micrometers allow for the spatially and time resolved study of boundary effects. Whereas long-ranged diffusive charge carrier transport is observed within single crystals, no detectable diffusive transport occurs across grain boundaries. The observed PL transients are found to crucially depend on the microscopic geometry of the crystal and the point of observation. In particular, spatially restricted diffusion of charge carriers leads to slower PL decay near crystal edges as compared to the crystal center. In contrast to many reports in the literature, our experimental results show no quenching or additional loss channels due to grain boundaries for the studied material, which thus do not negatively affect the performance of the derived thin-film devices.


Publication metadata

Author(s): Ciesielski R, Schafer F, Hartmann NF, Giesbrecht N, Bein T, Docampo P, Hartschuh A

Publication type: Article

Publication status: Published

Journal: ACS Applied Materials and Interfaces

Year: 2018

Volume: 10

Issue: 9

Pages: 7974-7981

Print publication date: 07/03/2018

Online publication date: 13/02/2018

Acceptance date: 13/02/2018

Date deposited: 25/04/2018

ISSN (print): 1944-8244

ISSN (electronic): 1944-8252

Publisher: American Chemical Society

URL: https://doi.org/10.1021/acsami.7b17938

DOI: 10.1021/acsami.7b17938


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